A switched-mode power supply (switching-mode supply, switch-mode switched SMPS, or switcher) is an electronic that incorporates a switching regulator to convert electrical efficiently. Like other supplies, SMPS transfers from DC AC source (often mains power, see adapter) loads, such as personal computer, while converting voltage and current characteristics. Unlike linear the pass transistor of switching-mode continually switches between low-dissipation, full-on full-off states, spends very little time in high dissipation transitions, which minimizes wasted energy. hypothetical ideal dissipates no power. Voltage regulation achieved by varying ratio on-to-off (also known duty cycles). In contrast, regulates output dissipating transistor. This higher conversion efficiency important advantage supply. Switched-mode supplies can also be substantially smaller lighter than because transformer much smaller. it operates on frequency ranges several hundred kHz MHz contrast 50-60Hz typical for frequency. Despite reduction size, topology itself requirement electromagnetic interference suppression commercial designs result usually greater component count corresponding circuit complexity. Switching regulators are used replacements when efficiency, size weight required. They are, however, more complicated; currents cause noise problems if not carefully suppressed, simple may have poor factor.